The subject of endoprosthetic joints has received a great deal of attention over the past several years and has particularly received much attention in recent years due in part to the availability of improved materials inert to human or animal bodies and to improved techniques for manipulating same. However, in spite of such intensive study, the endoprosthetic joints previously available, while in many cases satisfactory to a limited degree, are far from fully satisfactory and intensive work is continuing for the further improvement of such prostheses.
In one particular area, namely that of the ginglymus joints found in phalangeal joints and in the metacarpol phalangeal joint, previous efforts, while considerable and to a degree satisfactory, have still left considerable to be desired. Among the problems to be faced in connection with such joints, it is necessary to provide a joint which permits motion in only one plane and which to this end will have a considerable amount of resistance against motion out of such plane. For example, in many finger manipulations, considerable side pressure is placed upon the ends of the fingers, and especially on the thumb by the forefinger in some grasping manipulations, and the endoprosthetic joint must be able to resist such force. On the other hand, in such cases where during the implanting procedure it is preferable to implant each part of the joint separately, it is necessary that the two parts can be snapped together with a minimum of effort after the implanting has been completed.
In my earlier U.S. Pat. No. 3,506,982, I dealt with this same problem and provided a joint designed for movement in only a single plane together with means by which same could be firmly and reliably implanted into appropriate bones on either side of a ginglymus, as a phalangeal, joint. Endoprosthetic joints made according to this patent have proven extremely successful and have been implanted successfully in large numbers. However, in a continuing effort to improve products of this nature and recognizing that the joint of U.S. Pat. No. 3,506,982 normally provides for at least a limited degree of adduction and abduction, I have now developed a joint wherein the motion is firmly confined to a single plane and no abduction or adduction whatever is permitted. In this connection, I have proceeded from the broad suggestion contained in said patent relative to utilizing a more cylindrical protuberant head than set forth in such patent and have now developed same fully to an operative form and disclose same herewith.
Accordingly, the objectives of the invention include:
1. To provide a prosthesis for ginglymus joints which can be assembled or disassembled as needed during the implanting procedures but when assembled will provide strong resistance against a laterally applied force.
2. To provide a prosthesis, as aforesaid, which will be of sufficiently simple design as to be readily made by normal manufacturing procedures.
3. To provide a prosthesis, as aforesaid, which can be readily and easily implanted into bone structure on either side of a joint, such as a phalangeal joint.
4. To provide a prosthesis, as aforesaid, which will be strong and sturdy in operation and enable the user to perform all normal finger functions.
5. To provide a prosthesis, as aforesaid, which closely approximates the normal phalangeal joints.
Other objects and purposes of the invention will be apparent to persons acquainted with devices of this general type upon reading the following specification and inspection of the accompanying drawings.